Have 2 of these and really dig everything about them

Easy to disassemble, clean, build, reassemble, fill, and a joy to vape with on every APV I own. Very reliable and rock-steady for Ti TC. Holds enough Juice to run most all day out and about or at work (sometimes topping off toward the end of the work day). Size and Aesthetics are nice (IMO).
Perfect (as I "wish" they were) ? No. But, quite close enough. Never a Dry-Hit. Very very limited "seepage" from the AF (typically only a tad every now and then after a re-fill) but no "leakage". The Flavor is Amazing (only beaten by my Tengu) and YES,,, it takes ample Liquid vaporizing to make "great Flavor" same as it takes ample Fuel to produce big Horsepower. If you think the Bellus drinks the Juice, you should try a Tengu.
I build them in single-Coil Config (to get desired @ 0.26 R using Ti) with 26ga Ti, slightly spaced 6 wrap on a 2.38mm I.D. horizontal and position the Coils toward the top to a tad above the AF Intake as suggested by others here. I have built centered on the AF as well and have found, at least IMO and in all my experiences, slightly to the top and above the AF to be superior to centered for Flavor. I use all 70/30 or 80/20 mix Liquids.
It is tight to get that Build in there properly but not a real Issue.
Wicking isn't difficult once you consider the Design of the Deck/Base and how it all comes together and is meant to work. As Croak said, not too much, not too little and not all the way down to the Base but terminating at the Build-Deck "Step". Just enough side-to-side to cover that Step Area but not "stuffing" it or packed tight. I have also experimented with leaving a little longer "tail" (very light in material) in the middle of the Wick "Brush" that extends down onto the lower Juice Slot at the Base covering about 1/2 of that. Takes more time and effort but once I did that, it seemed to reduce the "seepage" after re-fill with no negative effects on Juice feed or decrease in Flavor or propensity to lean-hit.
Also, a much forgotten aspect of Wicking (it seems) is the proper amount/diameter of Wicking inside the Coil itself. Especially taking into consideration the Material you use. I use OC and get it just barely enough (diameter of Wick) to provide some resistance when sliding back and forth through the Coil to be sufficient knowing it will "swell" when soaked. Too much/packed and it will become "choked-off" backing up Juice into the Chimney/Chamber area leading to flooding and lean/dry hits. Too little and it (that portion of the Wick) will burn through prematurely and/or waste Juice by leaking or getting sucked up into the vapor tube (spit-back).
Vaping is quite similar to Internal Combustion Engine Dynamic in that it takes optimal Air-Fuel/Juice mix Tuning, Design, and Delivery to achieve the maximum in performance from any Rig.
As for Vertical vs. Horizontal Coils,,, to Each-their own. Personally on the Bellus, I see absolutely zero reason or advantage to Verticals and will stick to Horizontal. Then again, the Single Horizontal 2.38mm I.D. 6 wrap 26 ga Ti Builds I use and prefer perform great with zero Issue or Negative for my tastes and purposes. Others may use and prefer different Wire, Resistances, etc. that may necessitate a Vertical to fit.
That's just the way I do things on my Bellus(s) and what comes from it. Your "mileage" may vary and that's cool
For some reason, have never taken Pics of the Steps during my Build Process on the Bellus as have with other RTAs or would post some.